The present invention pertains generally to round stops for automatic weapons, and pertains in particular to a timed round stop for a sprocket fed weapon.
In one type of conventional machine gun feeder, ammunition linked together to form a belt is fed into the weapon by means of a single feed sprocket. The feed sprocket rotates, each tooth thereof engaging one round and pushing the round into engagement with the stripper bolt at a feed transfer position. The stripper bolt is a reciprocating element which delivers each round in sequence to be chambered and fired. As the stripper bolt moves the round from the feed transfer position, fixed guide surfaces which are associated with the stripper bolt engage the links that join each round to the next and strip them off the round for ejection from the weapon. Because the stripper bolt is a reciprocating element, it can accept a round of ammunition only while in the feed transfer position. If the round fed by the feed sprocket arrives at the feed transfer position before the stripper bolt, a feed jam occurs.
This problem is accentuated in weapons, such as the GE-150, made by the General Electric Co., that are equipped with feeders designed to accept ammunition linked with either of two different links, such as the M-9 link and the M15A2 link. The feed sprocket teeth are designed to fit tightly between rounds linked with the shorter-pitched link, in the case of the example the M-9 link, to maximize round control and minimize the above-described problem. The pitch of the M15A2 link is about 0.090 inch greater than that of the M-9 link, which results in reduced round control when the M15A2 link is employed. It is desirable to avoid the need for additional round control devices and separate feed sprockets for each link.
A related problem occurs during loading of the weapon. When rounds are loaded into weapons such as the GE-150, the feed sprocket is disengaged from its driver so that it can turn freely. During the loading the lead round could accidentally be inserted manually as far as the feed transfer location. This is undesirable since the stripper bolt may not be in the correct position to receive a round, resulting in a feed jam.
Round stops that cooperate with the feed sprocket to prevent these problems are well known. One typical arrangement is the GE-120C feeder, made by the General Electric Co., in which belted ammunition is fed from one of two feed sprockets to a feed tray in the bottom of the feeder. A spring-loaded round stop forces the round into a special slot and holds it there until the round is rammed into the chamber by the bolt.
Another anti-jam device is disclosed in U.S. Pat. No. 2,820,401, issued Jan. 21, 1958, to J. Gerick, for Machine Gun Anti-Jamming Device. In this device, a spring-loaded depressor which normally protrudes into the ammunition feed path is forced out of the path by the end of each tooth of the feed sprocket. A coil spring returns the depressor to its normal position after the sprocket tooth has cleared the depressor.
Conventional depressors and round stops typically rely on spring energy for at least half of their actuation cycle. For a high reliability weapon, this is undesirable, because the extreme vibrational loading that occurs during firing can cause a loss of round control and result in a malfunction. Moreover, any given conventional device is only suited for use with rounds linked together with a single pitch.